The origins of unpredictability in life outcome prediction tasks.

Why are some life outcomes difficult to predict? We investigated this question through in-depth qualitative interviews with 40 families sampled from a multidecade longitudinal study. Our sampling and interviewing process was informed by the earlier efforts of hundreds of researchers to predict life outcomes for participants in this study. The qualitative evidence we uncovered in these interviews combined with a mathematical decomposition of prediction error led us to create a conceptual framework. Our specific evidence and our more general framework suggest that unpredictability should be expected in many life outcome prediction tasks, even in the presence of complex algorithms and large datasets. Our work provides a foundation for future empirical and theoretical work on unpredictability in human lives.

Identifying gaps in parental support for families of children with hypoplastic left heart syndrome.

PURPOSE: The purpose of this study is to identify gaps in support for parents of children with Hypoplastic Left Heart Syndrome. DESIGN AND METHODS: Using a mixed-methods approach, the researchers first studied the parental and care team experience through interviews of Hypoplastic Left Heart Syndrome mothers and members of the inter-professional care team and then conducted an international survey of 690 Hypoplastic Left Heart Syndrome primary caregivers to validate the qualitative findings. RESULTS: Parental and care team interviews revealed three main gaps in parental support, including lack of open communication, unrealistic parental expectations, and unclear inter-professional team roles. Survey results found that parents whose children were diagnosed with Hypoplastic Left Heart Syndrome after birth indicated significant dissatisfaction with the care team's open communication and welcoming of feedback (p = 0.008). As parents progress through the stages of surgical intervention, they also indicate significant dissatisfaction with the care team's anticipation of parental emotional needs and provision of coping resources (p = 0.003). CONCLUSIONS: Parental support interventions should focus on providing resources to help parents cope, helping the care team model open communication, and welcoming feedback on the parental experience. PRACTICE IMPLICATIONS: Interventions should be piloted with parents who are in the later stages of the surgical intervention timeline or whose children were diagnosed after birth as they are the populations who perceived the least support within this study.

Model system identification of novel congenital heart disease gene candidates: focus on RPL13.

Genetics is a significant factor contributing to congenital heart disease (CHD), but our understanding of the genetic players and networks involved in CHD pathogenesis is limited. Here, we searched for de novo copy number variations (CNVs) in a cohort of 167 CHD patients to identify DNA segments containing potential pathogenic genes. Our search focused on new candidate disease genes within 19 deleted de novo CNVs, which did not cover known CHD genes. For this study, we developed an integrated high-throughput phenotypical platform to probe for defects in cardiogenesis and cardiac output in human induced pluripotent stem cell (iPSC)-derived multipotent cardiac progenitor (MCPs) cells and, in parallel, in the Drosophila in vivo heart model. Notably, knockdown (KD) in MCPs of RPL13, a ribosomal gene and SON, an RNA splicing cofactor, reduced proliferation and differentiation of cardiomyocytes, while increasing fibroblasts. In the fly, heart-specific RpL13 KD, predominantly at embryonic stages, resulted in a striking 'no heart' phenotype. KD of Son and Pdss2, among others, caused structural and functional defects, including reduced or abolished contractility, respectively. In summary, using a combination of human genetics and cardiac model systems, we identified new genes as candidates for causing human CHD, with particular emphasis on ribosomal genes, such as RPL13. This powerful, novel approach of combining cardiac phenotyping in human MCPs and in the in vivo Drosophila heart at high throughput will allow for testing large numbers of CHD candidates, based on patient genomic data, and for building upon existing genetic networks involved in heart development and disease.

Natural underlying mtDNA heteroplasmy as a potential source of intra-person hiPSC variability.

Functional variability among human clones of induced pluripotent stem cells (hiPSCs) remains a limitation in assembling high-quality biorepositories. Beyond inter-person variability, the root cause of intra-person variability remains unknown. Mitochondria guide the required transition from oxidative to glycolytic metabolism in nuclear reprogramming. Moreover, mitochondria have their own genome (mitochondrial DNA [mtDNA]). Herein, we performed mtDNA next-generation sequencing (NGS) on 84 hiPSC clones derived from a cohort of 19 individuals, including mitochondrial and non-mitochondrial patients. The analysis of mtDNA variants showed that low levels of potentially pathogenic mutations in the original fibroblasts are revealed through nuclear reprogramming, generating mutant hiPSCs with a detrimental effect in their differentiated progeny. Specifically, hiPSC-derived cardiomyocytes with expanded mtDNA mutations non-related with any described human disease, showed impaired mitochondrial respiration, being a potential cause of intra-person hiPSC variability. We propose mtDNA NGS as a new selection criterion to ensure hiPSC quality for drug discovery and regenerative medicine.

Addressing Variability and Heterogeneity of Induced Pluripotent Stem Cell-Derived Cardiomyocytes.

Induced pluripotent stem cells (iPSCs) offer great promise in the areas of disease modeling, basic research, drug development, and regenerative medicine. Much of their value comes from the fact that they can be used to create otherwise inaccessible cell types, such as cardiomyocytes, which are genetically matched to a patient or any other individual of interest. A consistent issue plaguing the iPSC platform, however, involves excessive variability exhibited in the differentiated products. This includes discrepancies in genetic, epigenetic, and transcriptional features, cell signalling, the cell types produced from cardiac differentiation, and cardiomyocyte functionality. These properties can result from both the somatic source cells and environmental conditions related to the derivation and handling of these cells. Understanding the potential sources of variability, along with determining which factors are most relevant to a given application, are essential in advancing iPSC-based technologies.

Loss of Ventricular Function After Bidirectional Cavopulmonary Connection: Who Is at Risk?

Decline of single ventricle systolic function after bidirectional cavopulmonary connection (BDCPC) is thought to be a transient phenomenon. We analyzed ventricular function after BDCPC according to ventricular morphology and correlated this evolution to long-term prognosis. A review from Mayo Clinic databases was performed. Visually estimated ejection fraction (EF) was reported from pre-BDCPC to pre-Fontan procedure. The last cardiovascular update was collected to assess long-term prognosis. A freedom from major cardiac event survival curve and a risk factor analysis were performed. 92 patients were included; 52 had left ventricle (LV) morphology and 40 had right ventricle (RV) morphology (28/40 had hypoplastic left heart syndrome (HLHS)). There were no significant differences in groups regarding BDCPC procedure or immediate post-operative outcome. EF showed a significant and relevant decrease from baseline to discharge in the HLHS group: 59 ± 4% to 49 ± 7% or - 9% (p < 0.01) vs. 58 ± 3% to 54 ± 6% or - 4% in the non-HLHS RV group (p = 0.04) and 61 ± 4% to 60 ± 4% or - 1% in the LV group (p = 0.14). Long-term recovery was the least in the HLHS group: EF prior to Fontan 54 ± 2% vs. 56 ± 6% and 60 ± 4%, respectively (p < 0.01). With a median follow-up of 8 years post-BDCPC, six patients had Fontan circulation failure, four died, and three had heart transplantation. EF less than 50% at hospital discharge after BDCPC was strongly correlated to these major cardiac events (HR 3.89; 95% Cl 1.04-14.52). Patients with HLHS are at great risk of ventricular dysfunction after BDCPC. This is not a transient phenomenon and contributes to worse prognosis.

Hypoplastic left heart syndrome: From bedside to bench and back.

Hypoplastic Left Heart Syndrome (HLHS) is a complex Congenital Heart Disease (CHD) that was almost universally fatal until the advent of the Norwood operation in 1981. Children with HLHS who largely succumbed to the disease within the first year of life, are now surviving to adulthood. However, this survival is associated with multiple comorbidities and HLHS infants have a higher mortality rate as compared to other non-HLHS single ventricle patients. In this review we (a) discuss current clinical challenges associated in the care of HLHS patients, (b) explore the use of systems biology in understanding the molecular framework of this disease, (c) evaluate induced pluripotent stem cells as a translational model to understand molecular mechanisms and manipulate them to improve outcomes, and (d) investigate cell therapy, gene therapy, and tissue engineering as a potential tool to regenerate hypoplastic cardiac structures and improve outcomes.

Current Interventional and Surgical Management of Congenital Heart Disease: Specific Focus on Valvular Disease and Cardiac Arrhythmias.

Successful outcome in the care of patients with congenital heart disease depends on a comprehensive multidisciplinary team. Surgery is offered for almost every heart defect, despite complexity. Early mortality for cardiac surgery in the neonatal period is ≈10% and beyond infancy is <5%, with 90% to 95% of patients surviving with a good quality of life into the adult years. Advances in imaging have facilitated accurate diagnosis and planning of interventions and surgical procedures. Similarly, advances in the perioperative medical management of patients, particularly with intensive care, has also contributed to improving outcomes. Arrhythmias and heart failure are the most common late complications for the majority of defects, and reoperation for valvar problems is common. Lifelong surveillance for monitoring of recurrent or residual structural heart defects, as well as periodic assessment of cardiac function and arrhythmia monitoring, is essential for all patients. The field of congenital heart surgery is poised to incorporate new innovations such as bioengineered cells and scaffolds that will iteratively move toward bioengineered patches, conduits, valves, and even whole organs.

Modeling structural and functional deficiencies of RBM20 familial dilated cardiomyopathy using human induced pluripotent stem cells.

Dilated cardiomyopathy (DCM) is a leading cause of heart failure. In families with autosomal-dominant DCM, heterozygous missense mutations were identified in RNA-binding motif protein 20 (RBM20), a spliceosome protein induced during early cardiogenesis. Dermal fibroblasts from two unrelated patients harboring an RBM20 R636S missense mutation were reprogrammed to human induced pluripotent stem cells (hiPSCs) and differentiated to beating cardiomyocytes (CMs). Stage-specific transcriptome profiling identified differentially expressed genes ranging from angiogenesis regulator to embryonic heart transcription factor as initial molecular aberrations. Furthermore, gene expression analysis for RBM20-dependent splice variants affected sarcomeric (TTN and LDB3) and calcium (Ca(2+)) handling (CAMK2D and CACNA1C) genes. Indeed, RBM20 hiPSC-CMs exhibited increased sarcomeric length (RBM20: 1.747 ± 0.238 µm versus control: 1.404 ± 0.194 µm; P < 0.0001) and decreased sarcomeric width (RBM20: 0.791 ± 0.609 µm versus control: 0.943 ± 0.166 µm; P < 0.0001). Additionally, CMs showed defective Ca(2+) handling machinery with prolonged Ca(2+) levels in the cytoplasm as measured by greater area under the curve (RBM20: 814.718 ± 94.343 AU versus control: 206.941 ± 22.417 AU; P < 0.05) and higher Ca(2+) spike amplitude (RBM20: 35.281 ± 4.060 AU versus control:18.484 ± 1.518 AU; P < 0.05). ß-adrenergic stress induced with 10 µm norepinephrine demonstrated increased susceptibility to sarcomeric disorganization (RBM20: 86 ± 10.5% versus control: 40 ± 7%; P < 0.001). This study features the first hiPSC model of RBM20 familial DCM. By monitoring human cardiac disease according to stage-specific cardiogenesis, this study demonstrates RBM20 familial DCM is a developmental disorder initiated by molecular defects that pattern maladaptive cellular mechanisms of pathological cardiac remodeling. Indeed, hiPSC-CMs recapitulate RBM20 familial DCM phenotype in a dish and establish a tool to dissect disease-relevant defects in RBM20 splicing as a global regulator of heart function.

NOTCH1-Dependent Nitric Oxide Signaling Deficiency in Hypoplastic Left Heart Syndrome Revealed Through Patient-Specific Phenotypes Detected in Bioengineered Cardiogenesis.

Hypoplastic left heart syndrome (HLHS) is a severe congenital heart defect (CHD) attributable to multifactorial molecular underpinnings. Multiple genetic loci have been implicated to increase the risk of disease, yet genotype-phenotype relationships remain poorly defined. Whole genome sequencing complemented by cardiac phenotype from five individuals in an HLHS-affected family enabled the identification of NOTCH1 as a prioritized candidate gene linked to CHD in three individuals with mutant allele burden significantly impairing Notch signaling in the HLHS-affected proband. To better understand a mechanistic basis through which NOTCH1 contributes to heart development, human induced pluripotent stem cells (hiPSCs) were created from the HLHS-affected parent-proband triad and differentiated into cardiovascular cell lineages for molecular characterization. HLHS-affected hiPSCs exhibited a deficiency in Notch signaling pathway components and a diminished capacity to generate hiPSC-cardiomyocytes. Optimization of conditions to procure HLHS-hiPSC-cardiomyocytes led to an approach that compensated for dysregulated nitric oxide (NO)-dependent Notch signaling in the earliest specification stages. Augmentation of HLHS-hiPSCs with small molecules stimulating NO signaling in the first 4 days of differentiation provided a cardiomyocyte yield equivalent to the parental hiPSCs. No discernable differences in calcium dynamics were observed between the bioengineered cardiomyocytes derived from the proband and the parents. We conclude that in vitro modeling with HLHS-hiPSCs bearing NOTCH1 mutations facilitated the discovery of a NO-dependent signaling component essential for cardiovascular cell lineage specification. Potentiation of NO signaling with small therapeutic molecules restored cardiogenesis in vitro and may identify a potential therapeutic target for patients affected by functionally compromised NOTCH1 variants. Stem Cells 2017;35:1106-1119.

Fathers' Perceived Reasons for Their Underrepresentation in Child Health Research and Strategies to Increase Their Involvement.

Purpose Examine fathers' perceived reasons for their lack of inclusion in pediatric research and strategies to increase their participation. Description We conducted expert interviews with researchers and practitioners (N = 13) working with fathers to inform the development of an online survey. The survey-which measured fathers' perceived reasons for their underrepresentation in pediatric research, recommended recruitment venues, and research personnel and study characteristics valued by fathers-was distributed online and in-person to fathers. Assessment Respondents included 303 fathers. Over 80 % of respondents reported that fathers are underrepresented in pediatric research because they have not been asked to participate. Frequently recommended recruitment venues included community sports events (52 %), social service programs (48 %) and the internet (60 %). Compared with white fathers, more non-white fathers recommended public transit (19 % vs. 10 %, p = .02), playgrounds (16 % vs. 6 %, p = .007) and barber shops (34 % vs. 14 %, p < .0001) and fewer recommended doctors' offices (31 % vs. 43 %, p = .046) as recruitment venues. Compared with residential fathers (100 % resident with the target child), more non-residential fathers recommended social services programs (45 % vs. 63 %, p = .03) and public transit (10 % vs. 27 %, p = .001) and fewer recommended the workplace (17 % vs. 40 %, p = .002) as recruitment venues. Study brevity, perceived benefits for fathers and their families, and the credibility of the lead organization were valued by fathers. Conclusion Fathers' participation in pediatric research may increase if researchers explicitly invite father to participate, target father-focused recruitment venues, clearly communicate the benefits of the research for fathers and their families and adopt streamlined study procedures.

Rbm20-deficient cardiogenesis reveals early disruption of RNA processing and sarcomere remodeling establishing a developmental etiology for dilated cardiomyopathy.

Dilated cardiomyopathy (DCM) due to mutations in RBM20, a gene encoding an RNA-binding protein, is associated with high familial penetrance, risk of progressive heart failure and sudden death. Although genetic investigations and physiological models have established the linkage of RBM20 with early-onset DCM, the underlying basis of cellular and molecular dysfunction is undetermined. Modeling human genetics using a high-throughput pluripotent stem cell platform was herein designed to pinpoint the initial transcriptome dysfunction and mechanistic corruption in disease pathogenesis. Tnnt2-pGreenZeo pluripotent stem cells were engineered to knockdown Rbm20 (shRbm20) to determine the cardiac-pathogenic phenotype during cardiac differentiation. Intracellular Ca(2+) transients revealed Rbm20-dependent alteration in Ca(2+) handling, coinciding with known pathological splice variants of Titin and Camk2d genes by Day 24 of cardiogenesis. Ultrastructural analysis demonstrated elongated and thinner sarcomeres in the absence of Rbm20 that is consistent with human cardiac biopsy samples. Furthermore, Rbm20-depleted transcriptional profiling at Day 12 identified Rbm20-dependent dysregulation with 76% of differentially expressed genes linked to known cardiac pathology ranging from primordial Nkx2.5 to mature cardiac Tnnt2 as the initial molecular aberrations. Notably, downstream consequences of Rbm20-depletion at Day 24 of differentiation demonstrated significant dysregulation of extracellular matrix components such as the anomalous overexpression of the Vtn gene. By using the pluripotent stem cell platform to model human cardiac disease according to a stage-specific cardiogenic roadmap, we established a new paradigm of familial DCM pathogenesis as a developmental disorder that is patterned during early cardiogenesis and propagated with cellular mechanisms of pathological cardiac remodeling.

Nos3-/- iPSCs model concordant signatures of in utero cardiac pathogenesis.

BACKGROUND: Through genome-wide transcriptional comparisons, this study interrogates the capacity of in vitro differentiation of induced pluripotent stem cells (iPSCs) to accurately model pathogenic signatures of developmental cardiac defects. METHODS AND RESULTS: Herein, we studied the molecular etiology of cardiac defects in Nos3(-/-) mice via transcriptional analysis of stage-matched embryonic tissues and iPSC-derived cells. In vitro comparisons of differentiated cells were calibrated to in utero benchmarks of health and disease. Integrated systems biology analysis of WT and Nos3(-/-) transcriptional profiles revealed 50% concordant expression patterns between in utero embryonic tissues and ex vivo iPSC-derived cells. In particular, up-regulation of glucose metabolism (p-value=3.95×10(-12)) and down-regulation of fatty acid metabolism (p-value=6.71×10(-12)) highlight a bioenergetic signature of early Nos3 deficiency during cardiogenesis that can be recapitulated in iPSC-derived differentiated cells. CONCLUSIONS: The in vitro concordance of early Nos3(-/-) disease signatures supports the utility of iPSCs as a cellular model of developmental heart defects. Moreover, this study supports the use of iPSCs as a platform to pinpoint initial stages of congenital cardiac pathogenesis.

Compound heterozygous NOTCH1 mutations underlie impaired cardiogenesis in a patient with hypoplastic left heart syndrome.

Hypoplastic left heart syndrome (HLHS) is a severe congenital heart defect (CHD) that necessitates staged, single ventricle surgical palliation. An increased frequency of bicuspid aortic valve (BAV) has been observed among relatives. We postulated number of mutant alleles as a molecular basis for variable CHD expression in an extended family comprised of an HLHS proband and four family members who underwent echocardiography and whole-genome sequencing (WGS). Dermal fibroblast-derived induced pluripotent stem cells (iPSC) were procured from the proband-parent trio and bioengineered into cardiomyocytes. Cardiac phenotyping revealed aortic valve atresia and a slit-like left ventricular cavity in the HLHS proband, isolated bicuspid pulmonary valve in his mother, BAV in a maternal 4° relative, and no CHD in his father or sister. Filtering of WGS for rare, functional variants that segregated with CHD and were compound heterozygous in the HLHS proband identified NOTCH1 as the sole candidate gene. An unreported missense mutation (P1964L) in the cytoplasmic domain, segregating with semilunar valve malformation, was maternally inherited and a rare missense mutation (P1256L) in the extracellular domain, clinically silent in the heterozygous state, was paternally inherited. Patient-specific iPSCs exhibited diminished transcript levels of NOTCH1 signaling pathway components, impaired myocardiogenesis, and a higher prevalence of heterogeneous myofilament organization. Extended, phenotypically characterized families enable WGS-derived variant filtering for plausible Mendelian modes of inheritance, a powerful strategy to discover molecular underpinnings of CHD. Identification of compound heterozygous NOTCH1 mutations and iPSC-based functional modeling implicate mutant allele burden and impaired myogenic potential as mechanisms for HLHS.

Selection via pluripotency-related transcriptional screen minimizes the influence of somatic origin on iPSC differentiation propensity.

The value of induced pluripotent stem cells (iPSCs) within regenerative medicine is contingent on predictable and consistent iPSC differentiation. However, residual influence of the somatic origin or reprogramming technique may variegate differentiation propensity and confound comparative genotype/phenotype analyses. The objective of this study was to define quality control measures to select iPSC clones that minimize the influence of somatic origin on differentiation propensity independent of the reprogramming strategy. More than 60 murine iPSC lines were derived from different fibroblast origins (embryonic, cardiac, and tail tip) via lentiviral integration and doxycycline-induced transgene expression. Despite apparent equivalency according to established iPSC histologic and cytomorphologic criteria, clustering of clonal variability in pluripotency-related gene expression identified transcriptional outliers that highlighted cell lines with unpredictable cardiogenic propensity. Following selection according to a standardized gene expression profile calibrated by embryonic stem cells, the influence of somatic origin on iPSC methylation and transcriptional patterns was negated. Furthermore, doxycycline-induced iPSCs consistently demonstrated earlier differentiation than lentiviral-reprogrammed lines using contractile cardiac tissue as a measure of functional differentiation. Moreover, delayed cardiac differentiation was predominately associated with upregulation in pluripotency-related gene expression upon differentiation. Starting from a standardized pool of iPSCs, relative expression levels of two pluripotency genes, Oct4 and Zfp42, statistically correlated with enhanced cardiogenicity independent of somatic origin or reprogramming strategy (R(2) = 0.85). These studies demonstrate that predictable iPSC differentiation is independent of somatic origin with standardized gene expression selection criteria, while the residual impact of reprogramming strategy greatly influences predictable output of tissue-specification required for comparative genotype/phenotype analyses.

New and TALENted genome engineering toolbox.

Recent advances in the burgeoning field of genome engineering are accelerating the realization of personalized therapeutics for cardiovascular disease. In the postgenomic era, sequence-specific gene-editing tools enable the functional analysis of genetic alterations implicated in disease. In partnership with high-throughput model systems, efficient gene manipulation provides an increasingly powerful toolkit to study phenotypes associated with patient-specific genetic defects. Herein, this review emphasizes the latest developments in genome engineering and how applications within the field are transforming our understanding of personalized medicine with an emphasis on cardiovascular diseases.

Transcriptome from circulating cells suggests dysregulated pathways associated with long-term recurrent events following first-time myocardial infarction.

BACKGROUND: Whole-genome gene expression analysis has been successfully utilized to diagnose, prognosticate, and identify potential therapeutic targets for high-risk cardiovascular diseases. However, the feasibility of this approach to identify outcome-related genes and dysregulated pathways following first-time myocardial infarction (AMI) remains unknown and may offer a novel strategy to detect affected expressome networks that predict long-term outcome. METHODS AND RESULTS: Whole-genome expression microarray on blood samples from normal cardiac function controls (n=21) and first-time AMI patients (n=31) within 48-hours post-MI revealed expected differential gene expression profiles enriched for inflammation and immune-response pathways. To determine molecular signatures at the time of AMI associated with long-term outcomes, transcriptional profiles from sub-groups of AMI patients with (n=5) or without (n=22) any recurrent events over an 18-month follow-up were compared. This analysis identified 559 differentially-expressed genes. Bioinformatic analysis of this differential gene-set for associated pathways revealed 1) increasing disease severity in AMI patients is associated with a decreased expression of genes involved in the developmental epithelial-to-mesenchymal transition pathway, and 2) modulation of cholesterol transport genes that include ABCA1, CETP, APOA1, and LDLR is associated with clinical outcome. CONCLUSION: Differentially regulated genes and modulated pathways were identified that were associated with recurrent cardiovascular outcomes in first-time AMI patients. This cell-based approach for risk stratification in AMI could represent a novel, non-invasive platform to anticipate modifiable pathways and therapeutic targets to optimize long-term outcome for AMI patients and warrants further study to determine the role of metabolic remodeling and regenerative processes required for optimal outcomes.

Transcriptional atlas of cardiogenesis maps congenital heart disease interactome.

Mammalian heart development is built on highly conserved molecular mechanisms with polygenetic perturbations resulting in a spectrum of congenital heart diseases (CHD). However, knowledge of cardiogenic ontogeny that regulates proper cardiogenesis remains largely based on candidate-gene approaches. Mapping the dynamic transcriptional landscape of cardiogenesis from a genomic perspective is essential to integrate the knowledge of heart development into translational applications that accelerate disease discovery efforts toward mechanistic-based treatment strategies. Herein, we designed a time-course transcriptome analysis to investigate the genome-wide dynamic expression landscape of innate murine cardiogenesis ranging from embryonic stem cells to adult cardiac structures. This comprehensive analysis generated temporal and spatial expression profiles, revealed stage-specific gene functions, and mapped the dynamic transcriptome of cardiogenesis to curated pathways. Reconciling known genetic underpinnings of CHD, we deconstructed a disease-centric dynamic interactome encoded within this cardiogenic atlas to identify stage-specific developmental disturbances clustered on regulation of epithelial-to-mesenchymal transition (EMT), BMP signaling, NF-AT signaling, TGFb-dependent EMT, and Notch signaling. Collectively, this cardiogenic transcriptional landscape defines the time-dependent expression of cardiac ontogeny and prioritizes regulatory networks at the interface between health and disease.